Scaling-up ecosystem functions of marine soft sediments combining field data and drone imagery.

Ecosystem services (ES) define the benefits deriving from natural resources and are useful for balancing human exploitative uses with the preservation of natural capital. Although the mapping of ES supply has become a common practice for terrestrial ecosystems, its application in marine ecosystems is hindered by inadequate knowledge of the distribution of communities and habitats and the ecosystem functions that they provide and by the difficulty to obtain high resolution data over large scales. In this regard, remote sensing offers the ability to collect data over large areas in a snapshot of time that can complement field-based sampling methods by extrapolating them into the wider spatial and temporal context. However, conventional remote sensing tools (i.e. satellite and aircraft imaging) provide data at limited spatial and temporal resolutions and relatively high costs for small-scale environmental science and ecologically-focussed studies. In this study, we describe a drone-based imaging system and mapping procedure that was developed for constructing high resolution ecosystem functioning models of intertidal soft sediments. Using regression analysis we studied the relationship between biogenic surface features in estuarine soft sediments and ecosystem functions in a heterogeneous landscape. We then mapped the distribution and abundance of biogenic features from drone-captured images of the sandflat to scale-up these relationships to the whole estuary. The image processing procedure uses automatic feature detection and matching and requires minimal human input. The resulting maps combine imagery and field data and show the distribution and quantification of a set of ecosystem functions at the scale of an estuary. Results of the system are presented for the intertidal flats at Whangateau Harbour, New Zealand.